Stainless Steel Counterparts Research Articles

Developing PMMA/Coffee Husk Green Composites to Meet the Individual Requirements of People with Disabilities: Hip Spacer Case Study

When replacing a damaged artificial hip joint, treatment involves using antibiotic-laced bone cement as a spacer. One of the most popular materials used for spacers is PMMA; however, it has limitations in terms of mechanical and tribological properties. To overcome such limitations, the current paper proposes utilizing a natural filler, coffee husk, as a reinforcement for PMMA. The coffee husk filler was first prepared using the ball-milling technique. PMMA composites with varying weight fractions of coffee husk (0, 2, 4, 6, and 8 wt.%) were prepared. The hardness was measured to estimate the mechanical properties of the produced composites, and the compression test was utilized to estimate the Young modulus and compressive yield strength. Furthermore, the tribological properties of the composites were evaluated by measuring the friction coefficient and wear by rubbing the composite samples against stainless steel and cow bone counterparts under different normal loads. The wear mechanisms were identified via scanning electron microscopy. Finally, a finite element model for the hip joint was built to investigate the load-carrying capacity of the composites under human loading conditions. The results show that incorporating coffee husk particles can enhance both the mechanical and tribological properties of the PMMA composites. The finite element results are consistent with the experimental findings, indicating the potential of the coffee husk as a promising filler material for enhancing the performance of PMMA-based biomaterials.

Improved tensile properties, stable microstructures and isotropic deformation of nanocrystalline 304 stainless steel

The tensile properties of nanocrystalline 304 stainless steel plate (NSSP-304) produced by severe rolling technology and its conventional polycrystalline 304 stainless steel (CPSS-304) counterpart were studied at room temperature. The microstructures of fractured NSSP-304 and CPSS-304 were characterized. NSSP-304 had enough ductility (elongation 34.5%), larger strengths, elastic strain and the reduction of area despite its smaller volume fraction of strain-induced α′-martensite (SIM) and no obvious work hardening. The deformation of NSSP-304 was more isotropic, its microstructures were more stable and homogeneous during tensile process due to the following results about fractured NSSP-304: (1) the narrower variation amplitude of surface micro-hardness along and perpendicular tensile directions; (2) the smaller void density and few surface micro-cracks; (3) the smaller surface roughness and roughness variation, and their narrower fluctuation ranges at three directions; (4) only micro-cracks without macro-cracks around NSSP-304 fracture; (5) its smaller volume fraction of SIM. The voids in CPSS-304 initiated around MnS inclusion, at grain boundaries, triple junctions, the boundaries of austenite and martensite phases, and in the two phases. They became micro-cracks within their original positions and macro-cracks by passing through different grains. The voids in NSSP-304 initiated at grain boundaries, triple junctions and the boundaries of the two phases. They became micro- and macro-cracks by passing through different grain boundaries. The MnS inclusion in NSSP-304 scarcely influenced its tensile deformation. The fracture mechanisms of NSSP-304 and CPSS-304 were the intergranular fracture, and the mixture of intergranular and transgranular fracture respectively.

Effect of environments on the tribological behaviour of pure and graphene coated nickel against stainless steel counterpart

Effect of environments on the tribological behaviour of pure and graphene coated nickel against stainless steel counterpart

Effect of environments on the tribological behavior of pure and graphene coated nickel against stainless steel counterpart

Effect of environments on the tribological behavior of pure and graphene coated nickel against stainless steel counterpart

Tribological Properties of Carbon Fiber-Reinforced PEEK against 304 Stainless Steel with Reticulate Surface Texture.

With the aim of improving the durability and reliability of polyetheretherketone (PEEK) composites reinforced with carbon fiber (CF) as thrust bearings without lubricants, a reticulate surface texture was fabricated by plane honing on a stainless steel (SS) counterpart to promote its tribological properties. Pin-on-disk experiments were designed, with the results showing that the reticulate surface texture effectively reduces the friction coefficient from 0.40 to 0.20 compared with the polished SS surface, within the range of the pv value from 0.185 to 1.85 MPa∙m/s. The wear mechanism of the polished SS surface against CF-PEEK, proven with SEM and EDS observations as well as AE measurements, is revealed, falling into abrasive wear with SS particles embedded in the friction interface around the CF strips, causing three-body contact. The reduction in the friction coefficient of the textured SS disk against the CF-PEEK pin can be achieved due to diminution of the CF wear debris and SS particles, which are scraped off by the groove edges and trapped by the groove valleys, reducing the three-body abrasive wear, while the honed plateau is used as a flank surface like a cutting tool to scratch more soft PEEK particles as the transferred film, owing to adhesive wear. This investigation suggests that the SS disk with a honed surface structure can be used as the counterpart of CF-PEEK bearings with a low friction coefficient and wear rate under dry friction.

Effect of ECR-glass additions in the mechanical and tribological properties of TiO2 reinforced polyimide composites

ABSTRACT The use of polyimide-reinforced composite materials in the design and fabrication of components for mechanical and tribological operation systems remains a research focus. As such, the present study investigated the effect of electrical corrosion resistance (ECR) glass on the mechanical and tribological properties of hybrid-polyimide composites using spark plasma sintering (SPS) method. The hardness and elastic modulus of the thermoplastic polyimide reinforced with TiO2 and ECR particles was investigated in this study with a nanoindentation tester under applied load of 200 mN. While the friction and wear behavior of the composites was ascertained with pin-on-disc tester under 10 N at 150 rpm with a stainless steel counterpart at room temperature. The results showed that the ECR glass addition remarkably improved the hardness and elastic modulus of the hybrid composites. Incorporation of the 10 wt% ECR glass effectively reduced the friction coefficient and wear rate by 55.5% and 92.2%, respectively, corroborating the potential of these ECR-TiO2-PI composites for applications requiring a low friction coefficient and wear rate with high mechanical properties.

Local–flexural interactive buckling behaviour and resistance of press-braked stainless steel slender channel section columns

The present paper reports experimental and numerical studies of the local–flexural interactive buckling behaviour and resistance of press-braked stainless steel slender channel section columns. A testing programme was firstly performed, including tensile coupon tests, initial geometric imperfection measurements and ten pin-ended column tests. The pin-ended column test setup, procedures and results were fully reported and analysed. The progression of local buckling and flexural buckling was discussed in detail. Following the testing programme, a numerical modelling programme was conducted, where finite element models were developed to replicate the test responses and then employed to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member effective lengths. The obtained test and numerical data were employed to assess the accuracy of the relevant design rules for press-braked stainless steel slender channel section columns, as set out in the European code, American specification and Australian/New Zealand standard. The assessment results revealed that the European code leads to conservative and scattered interactive buckling resistance predictions, while the American specification and Australian/New Zealand standard result in many unsafe and scattered interactive buckling resistance predictions. A new design approach was then developed, based on the Eurocode column buckling curve and the continuous strength method, and shown to lead to accurate, consistent and safe interactive buckling resistance predictions for press-braked stainless steel slender channel section columns. The reliability of the new design approach was confirmed by means of statical analyses. Besides, the relevant design rules for press-braked carbon steel slender channel section columns, as given in the North American specification, were assessed, and shown to result in unsafe though consistent interactive buckling resistance predictions, when used for their stainless steel counterparts.

Tribological behavior of CoCrFeNiMn high-entropy alloy against 304, Al2O3 and Si3N4 counterparts

Room-temperature (RT) dry sliding tribological behavior of CoCrFeNiMn high-entropy alloy (HEA) against 304 stainless steel (304), alumina (Al2O3) and silicon nitride (Si3N4) counterparts, and particularly the comparative 304/Al2O3 and 304/Si3N4 tribo-pairs were investigated. The HEA/304, HEA/Al2O3 and 304/Al2O3 tribo-pairs exhibit distinctly lower friction coefficient (μ) than HEA/Si3N4 and 304/Si3N4 tribo-pairs, while the trend of wear rate (W) is opposite. The similar structure of HEA and 304 leads to high mutual solubility and easy adhesion of the tribo-pair. Si3N4 has higher fracture toughness and lower hardness than Al2O3 ceramics and has better wear resistance. Therefore, the main wear mechanism of HEA or 304 was abrasive wear and adhesive wear when sliding against Al2O3, but oxidative wear and diffusion wear when sliding against Si3N4. Moreover, the HEA presents better tribological properties than 304 in terms of the wear rate of the disk and the counterpart when sliding against Si3N4, which can be attributed to the formation of more lubricating oxides induced by the tribo-chemical reaction such as Cr2O3, MnO2 and transfer layer SiOx on the worn surface.

The impact of low adsorption surfaces for the analysis of DNA and RNA oligonucleotides

As interest in oligonucleotide (ON) therapeutics is increasing, there is a need to develop suitable analytical methods able to properly analyze those molecules. However, an issue exists in the adsorption of ONs on different parts of the instrumentation during their analysis. The goal of the present paper was to comprehensively evaluate various types of bioinert materials used in ion-pairing reversed-phase (IP-RPLC) and hydrophilic interaction chromatography (HILIC) to mitigate this issue for 15- to 100-mer DNA and RNA oligonucleotides. The whole sample flow path was considered under both conditions, including chromatographic columns, ultra-high-performance liquid chromatography (UHPLC) system, and ultraviolet (UV) flow cell. It was found that a negligible amount of non-specific adsorption might be attributable to the chromatographic instrumentation. However, the flow cell of a detector should be carefully subjected to sample-based conditioning, as the material used in the UV flow cell was found to significantly impact the peak shapes of the largest ONs (60- to 100-mer). Most importantly, we found that the choice of column hardware had the most significant impact on the extent of non-specific adsorption. Depending on the material used for the column walls and frits, adsorption can be more or less pronounced. It was proved that any type of bioinert RPLC/HILIC column hardware offered some clear benefits in terms of adsorption in comparison to their stainless-steel counterparts. Finally, the evaluation of a large set of ONs was performed, including a DNA duplex and DNA or RNA ONs having different base composition, furanose sugar, and modifications occurring at the phosphate linkage or at the sugar moiety. This work represents an important advance in understanding the overall ON adsorption, and it helps to define the best combination of materials when analyzing a wide range of unmodified and modified 20-mer DNA and RNA ONs.

Experimental and numerical studies of stainless steel angle-to-plate connections

This paper presents experimental and numerical studies of stainless steel angle-to-plate connections failing by net section fracture. Tension tests were conducted on 16 austenitic stainless steel angle-to-plate connections, with each consisting of an equal-leg or unequal-leg angle section member bolted to gusset plates by one leg. The specimens were designed with different angle section sizes, number of bolt holes and connection lengths. The key test observed results, including the load–elongation curves as well as the failure loads and modes, were fully reported. The strain distribution at critical cross-sections and the effects of connection length, out-of-plane eccentricity and in-plane eccentricity on net section efficiency were discussed. The experimental programme was supplemented by a numerical modelling programme, where finite element models were firstly developed and validated against the test results and afterwards adopted to perform parametric studies to generate further numerical data. On the basis of the test and numerical data, the accuracy of the design rules for stainless steel angle-to-plate connections failing by net section fracture, as set out in the European code and American specification, was assessed. The assessment results revealed that the European code leads to excessively conservative and scattered failure load predictions, while the American specification yields unsafe failure load predictions. Therefore, an improved design approach was proposed and shown to provide substantially improved predictions of failure load over the design codes; the reliability of the proposed design approach was also demonstrated by statistical analyses. Besides, the existing codified and proposed design methods for carbon steel angle-to-plate connections were also assessed for their applicability to stainless steel angle-to-plate connections. It was found that the method specified in the American specification for carbon steel angle-to-plate​ connections can be safely extended to cover the design of their stainless steel counterparts.

Numerical Investigation of Composite Behavior and Strength of Rectangular Concrete-Filled Cold-Formed Steel Tubular Stub Columns.

The objective of this study was to investigate the composite behavior of rectangular concrete-filled cold-formed steel (CFS) tubular stub columns under axial compression. A fine finite 3D solid element model of rectangular concrete-filled cold-formed steel tubular stub column was established by ABAQUS, which utilized a constitutive model of cold-formed steel considering the cold-forming effect and a triaxial plastic-damage constitutive model of the infilled concrete. Good agreement was achieved and the average discrepancy between the experimental and FE results was less than 5%. Based on the verified models, a further parametric analysis was carried out to reveal the influence of various factors on the strength and behavior of the concrete-filled rectangular cold-formed steel tubular stub columns. The factors included constitutive models adopted for cold-formed steel, length over width ratio of the rectangular section, wall-thickness and width, and concrete strength and yield strength of the cold-formed steel. A total of 144 FE models were analyzed. The stress nephogram was reasonably simplified in accordance with the limit state and a theoretical formula considering confinement coefficient was proposed to estimate the ultimate bearing capacity of concrete-filled rectangular cold-formed steel tubular stub columns using the superposition method. The calculated results showed satisfactory agreement with both the experimental and FE results, which proved the validity and accuracy of the formula proposed in this paper. In the proposed formula, the confinement coefficient of square concrete-filled cold-formed steel tubular stub columns is larger than that of hot-rolled steel counterparts but smaller than that of the stainless steel counterparts.

Effect of Low Hydroxyapatite Loading Fraction on the Mechanical and Tribological Characteristics of Poly(Methyl Methacrylate) Nanocomposites for Dentures.

Denture base materials need appropriate mechanical and tribological characteristics to endure different stresses inside the mouth. This study investigates the properties of poly(methyl methacrylate) (PMMA) reinforced with different low loading fractions (0, 0.2, 0.4, 0.6, and 0.8 wt.%) of hydroxyapatite (HA) nanoparticles. HA nanoparticles with different loading fractions are homogenously dispersed in the PMMA matrix through mechanical mixing. The resulting density, Compressive Young’s modulus, compressive yield strength, ductility, fracture toughness, and hardness were evaluated experimentally; the friction coefficient and wear were estimated by rubbing the PMMA/HA nanocomposites against stainless steel and PMMA counterparts. A finite element model was built to determine the wear layer thickness and the stress distribution along the nanocomposite surfaces during the friction process. In addition, the wear mechanisms were elucidated via scanning electron microscopy. The results indicate that increasing the concentration of HA nanoparticles increases the stiffness, compressive yield strength, toughness, ductility, and hardness of the PMMA nanocomposite. Moreover, tribological tests show that increasing the nanoparticle weight fraction considerably decreases the friction coefficient and wear loss.

Deformation mechanics of self-expanding venous stents: Modelling and experiments

Deformation properties of venous stents based on braided design, chevron design, Z design, and diamond design are compared using in vitro experiments coupled with analytical and finite element modelling. Their suitability for deployment in different clinical contexts is assessed based on their deformation characteristics. Self-expanding stainless steel stents possess superior collapse resistance compared to Nitinol stents. Consequently, they may be more reliable to treat diseases like May-Thurner syndrome in which resistance against a concentrated (pinching) force applied on the stent is needed to prevent collapse. Braided design applies a larger radial pressure particularly for vessels of diameter smaller than 75% of its nominal diameter, making it suitable for a long lesion with high recoil. Z design has the least foreshortening, which aids in accurate deployment. Nitinol stents are more compliant than their stainless steel counterparts, which indicates their suitability in veins. The semi-analytical method presented can aid in rapid assessment of topology governed deformation characteristics of stents and their design optimization.

Biocompatibility and biodegradability evaluation of magnesium-based intramedullary bone implants in avian model.

At present days osteosynthesis modalities for avian fracture management are inadequate. External coaptation is the most practiced method however, specialized clinics have started introducing intramedullary pinning, external skeletal fixation with tie-in-fixation for fracture immobilization. Magnesium (Mg) based biomaterials are trustable developments in the field of orthopedics compared to their permanent stainless steel counterparts concerning long term adverse reaction. Mg implants are becoming promising for their use as intramedullary accessories because they are bioresorbable with high strength-weight ratio and the similarities in density and elastic modulus to the natural bones. However, their severe biodegradation trait restricts frequent use as load-bearing orthopedic implants. In this study, the biocompatibility and biodegradability of Mg based intramedullary cylindrical spacers (2.4 mm diameter × 8 mm height) reinforced with 0, 5, 15 wt% of hydroxyapatite (HA, Ca10 (PO4 )6 (OH)2 ) were evaluated in 18 Uttara-fowl birds. Clinical, radiological (from immediate postoperative days till 24th week), biochemical (first three postoperative weeks) and histopathological study of test bone were carried out to evaluate implant degradation and osteocompatibility. Biodegradation of Mg-3Zn/0HA and Mg-3Zn/15HA initiated a bit earlier at second week of implantation, while that of Mg-3Zn/5HA at 3-fourth week, and found biocompatible and biodegradable with no observable clinical and histopathological changes.

The contribution of orthodontic braces to aluminum exposure in humans: an experimental in vitro study.

There is limited information on whether metals such as aluminum (Al) can migrate from orthodontic braces to saliva and subsequently contribute to its exposure in humans. This study aimed to assess this experimentally by incubating elastomeric orthodontic ligatures in artificial saliva for 30days and other components of orthodontic braces (brackets, arch wires, and retainers) up to 180days. As demonstrated, significantly higher levels of Al were leached from elastomeric ligatures (mean ± SD 28.2 ± 6.8μg compared with their stainless steel counterparts (3.6± 0.1μg) during 30days. The higher the incubation time, the greater levels of Al leaching to artificial saliva were observed with the highest levels found for CNA β arch wire (252 ± 12μg), Ni-Ti-Al arch wire (224 ± 11μg), ceramic brackets (199 ± 10μg), stainless steel arch wire (108 ± 5μg), and metallic brackets (81.0 ± 4.2μg) after 180days of incubation. However, considering the tolerable weekly intake (TWI) established by the European Food Safety Authority, the intraoral use of orthodontic braces considered in this study would in the worst case constitute 0.04% and 0.09% of TWI in 70-kg adults and 30-kg children, respectively. In conclusion, the orthodontic braces considered in this study have no contribution to Al exposure in humans and can be considered safe in this regard.

Axial slenderness limits for austenitic stainless steel-concrete composite columns

The use of stainless steel in steel-concrete composite construction is an emerging topic considering the higher durability, corrosion resistance, and fire resistance as well as aesthetic benefits and ease of maintenance of stainless steel compared to carbon steel. In line with this, the present paper reports the results of a series of experimental and numerical investigations on the local and post-local buckling of austenitic stainless steel-concrete composite columns with an aim to propose axial slenderness limits as well as effective width/diameter formulae for these members. Such limits have not yet been established for stainless steel-concrete composite members in international design standards. Three section types, namely, concrete-filled box, concrete-filled circular, and partially-encased I-sections are thoroughly studied. The investigated columns include some of the largest and most slender stainless steel-concrete composite sections studied to date. The obtained results are compared with theory as well as approaches currently in use by international design standards. It is demonstrated that the codified slenderness limits developed for carbon steel-concrete composite columns cannot be directly used for the stainless steel counterparts and modifications are required. The modifications are recommended in light of the findings of the present study. In addition to axial slenderness limits, effective width/diameter formulae are also recommended for the studied section types.

A Comparison of the Compositional, Microstructural, and Mechanical Characteristics of Ni-Free and Conventional Stainless Steel Orthodontic Wires.

Ni-free orthodontic wires were introduced to mitigate concerns associated with the use of Ni-containing alloys in orthodontics. However, limited information is available on their properties and therefore, the aim of this study was to characterize the elemental composition, the microstructure, and the mechanical properties of Ni-free orthodontic wires and compare them with their stainless steel (SS) counterparts. Four Ni-free and four conventional SS wires were included in this study. All the wires were initially imaged with a Scanning Electron Microscopy (SEM) and their elemental compositions were determined by X-ray Energy Dispersive Spectroscopy (EDX). Then, their microstructure was assessed by X-ray Diffraction (XRD) and the indentation modulus, elastic index, Martens Hardness and Vickers Hardness by Instrumented Indentation Testing (IIT). All the wires demonstrated surface cracks and pores oriented parallel to their long axis. The elemental composition of Ni-free alloys showed an increased Mn and Cr content while both SS and Ni-free wires shared the same dominant austenite structure. In conclusion, despite the differences in elemental composition, Ni-free wires demonstrated a similar microstructure and comparable mechanical properties with their conventional SS counterparts and thus may be considered as a promising alternative for patients with Ni supersensitivity.

Synchronous optimization of strengths, ductility and corrosion resistances of bulk nanocrystalline 304 stainless steel

Structural materials usually suffer from several attacks during their service, such as tension, fatigue and corrosion. It is necessary to synchronously improve these properties for their lightweight and long-lifetime, but corrosion resistance and ductility are generally inverse correlation with strength, it is very difficult to simultaneously optimize all three properties. However, bulk nanocrystalline 304 stainless steel (BN-304SS) produced by severe rolling technology possessed the larger yield and ultimate tensile strengths with sufficient elongation (> 40%) during tensile test, the larger saturation stress and longer lifetime during low-cycle fatigue, the enhanced uniform and pitting corrosion resistances during five-day immersion test in 6 mol/L HCl, the lowered stress corrosion cracking (SCC) susceptibility with larger yield (∾2.40 GPa) and ultimate tensile (∾2.66 GPa) strengths, and enough elongation (> 30%) during stress corrosion in comparison with conventional polycrystalline 304 stainless steel (CP-304SS) counterpart. The uniform and pitting corrosion resistances of fractured BN-304SS were enhanced in comprsion with those of fractured CP-304SS during seven-day immersion test in 1 mol/L HCl. These results demonstrated the strengths, ductility and corrosion resistances of BN-304SS can be simultaneously optimized by severe rolling technology. These improved results of BN-304SS in different disciplines were understood by its valence electron configurations rather than traditional microstructural parameters.

Enhanced Passivation Layer by Cr Diffusion of 301 Stainless Steel Facilitated by SMAT

AISI 301 stainless steel (SS) is known for its high strength and hardness but tends to be less corrosion resistant for many applications. Several attempts have been made in the past to investigate its corrosion behavior by different methods. However, current knowledge is insufficient on its corrosion resistance when subjected to surface treatment. In this work, a new route to enhance the corrosion resistance of nanostructured 301 SS using surface mechanical attrition treatment (SMAT) method is described. SMAT improves the mechanical properties of 301 SS by the formation of a nanostructure layer on the material surface. Compared to the as‐received 316 and 304 SS counterparts, the present nanostructured 301 SS exhibits an improved corrosion behavior by a lower corrosion current density (1.308 mA/cm2), higher corrosion potential (−0.071 V), higher phase angle and impedance, better charge‐transfer resistance, and Cr content. The improved corrosion resistance can be attributed to the ability of SMAT to facilitate the move of Cr on the surface, which forms a stronger passivation layer with a new mechanism of passivation that may save a lot of noble metals.

The Effect of Al Addition on the Tribological Behavior of Ti−Si−Zr Alloys

While commercial biomedical titanium alloys present excellent biocompatibility and corrosion resistance, their poor wear resistance remains a major limitation. In this study, alloying with aluminum was used to improve the tribological performance of an experimental Ti−Si−Zr alloy. The effect of Al content on the alloy's microstructure and mechanical properties was evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Vickers hardness measurements. Sliding wear testing was performed in a ball-on-disk setup, using stainless steel and silicon nitride counterparts and serum solution lubrication. Microstructural examinations showed that an increase in Al content induced a change from eutectic cell microstructure to regular near-equiaxed particles and produced a solid solution strengthening, increasing alloy's hardness. The adhesive tendencies of the α-Ti matrix to the counterpart dominated the frictional response, and a lower friction coefficient was found against silicon nitride compared to stainless steel. In wear tests against stainless steel counterparts, the alloys showed significantly higher wear rates than the CoCr and Ti−6Al−4V references due to severe abrasive wear, induced by the adhesion of titanium matrix to the counterpart. The Al addition had a positive effect on the wear resistance against silicon nitride due to the solid solution strengthening and the change in microstructure, which reduced the risk of brittle delamination. However, while this gave a trend for a lower wear rate against silicon nitride than the Ti−6Al−4V alloy, the wear rate was still approximately three times higher than that of CoCr.